Friday, March 8, 2013

New computer models will help to monitor and predict the course of the disease

A bioscience response to ash dieback, a devastating disease caused by a fungal pathogen (Chalara fraxinea), that threatens our third most common broadleaf tree (after oak and birch), has been launched by the Biotechnology and Biological Sciences Research Council (BBSRC). University of Cambridge researchers, who have already been working closely with the government on the issue, will be an integral part of the initiative.

£2.4M of fast-track research funding has been awarded to gather an in-depth understanding of the ash dieback fungus and to provide genetic clues about some ash trees’ natural resistance to attack. Computer models will also be built to develop monitoring plans for the distribution and spread of the fungus, as well as charting how the disease might progress. This knowledge will help to fight the fungus and replace lost trees with those more able to survive.

Professor Christopher Gilligan with Drs Nik Cunniffe and Matt Castle at the University of Cambridge and Dr Frank van den Bosch at Rothamsted Research, have been awarded £1M in funding to develop and test mathematical, computer-based models to predict the spread of ash dieback in the UK, to improve strategies for surveillance and monitoring of the disease, and to inform ways to stop or delay the spread.

Professor Chris Gilligan, Head of the Epidemiology and Modelling group welcomed the award, saying: “This timely award will enable us to solve some of the fundamental epidemiological questions that underpin the ability of the UK to respond quickly and effectively to pest and disease incursions. The project is also designed to provide practical advice about the spread, where to sample, and the potential for management of ash dieback to policy makers and stakeholders throughout the course of the project.”

The ability to predict the future spread of an epidemic is crucial for designing both efficient sampling strategies and effective management plans. The use of models, informed by the most up-to-date data, allows different potential surveillance and management strategies to be explored in advance so the most effective ones can be identified and put into practice.

Specifically, using computational models for the spread of a pathogen provides a way to integrate information from the different strands of research (such as what environmental conditions are suitable for infection and how much of the ash tree population is resistant). This framework will allow management questions, such as “given the uncertainties involved, what control strategies would be effective?”, to be explored prior to the implementation of any given management program.

Dr Castle said: “This is an exciting opportunity for us; the award will allow us to build upon our existing modelling capabilities and explore even more sophisticated techniques for investigating the dynamics and future spread of ash dieback. This in turn will place us in an even stronger position to provide practical management advice.”

Dr Cunniffe said: "This award will allow us to develop epidemiological techniques and models applicable not only to ash dieback, but also to threats to our trees that we may face in the future."

The models will build on preliminary work by the Cambridge group to model the initial incursion of ash dieback and other diseases. Models of the patterns, causes, and effects of the disease will link with geographical information systems to predict the spread of disease across the UK landscapes.

The research will help inform where the disease is most likely to occur, where it will spread most rapidly and cause most damage, and where and when mitigation strategies should be most effectively used to slow or halt the spread. It will also help to answer key questions about monitoring the disease, such as: how to detect the disease in new areas early enough to control it; where to sample to find new outbreaks efficiently; and how we know if the disease is absent from an area.

The project will also look at how diseases might spread due to industries and trades involving trees and through atmospheric dispersal.

In addition to Cambridge, funding has been awarded to the Nornex consortium that brings together tree health and forestry specialists with scientists working with state-of-the-art genetic sequencing, biological data and imaging technologies to investigate the molecular and cellular basis of interactions between the fungus and ash trees.

Genome sequences of up to 30 samples of the fungus from the UK and Europe will rapidly help to acquire in-depth genetic information to shed light on the infection process. These data will reveal clues to the origins of the disease and provide genetic ‘markers’ to allow the spread of different strains of the fungus to be followed. Genetic data will also provide direct insights into the nature of the fungus.

The consortium will obtain information about how the disease spreads by studying infection in climate-controlled growth facilities, tracking the fungus as it colonises the plant. This vital information will help to develop effective disease control strategies.

The project will also uncover how some ash trees can partially resist attack. About 2% of Danish trees appear to ward off the disease but little information on the genetic basis for this is known. Genetic data from these trees will be compared to susceptible trees to find variations in their genetic codes. By identifying these differences, genetic makers can be developed to help breeders produce more resistant trees.

BBSRC Chief Executive Professor Douglas Kell said: “This agile funding response will ensure we improve our understanding of this devastating tree disease as quickly as possible. Little is known about the fungus, why it is so aggressive, or its interactions with the trees that it attacks. This prevents effective control strategies. These grants will enable the UK’s world-leading bioscience community to speed up the response to tackling the disease directly. It will also help us to understand and harness the ways in which some ash trees can defend themselves naturally.”